Sound-conducting tube



Amt-2o 1926.

I 1,581,734 w. HAHNEMANN ET AL souunconnucwme was Fi led August 25,1 192;

Patented Apr. 29, 1926.

untrue, sta rs FATENE' @FFEQE.

WALTER HAZ-ZNEllL'rlll'I-T, 0E KZTZEBEBG, NEAR KIEL, AND LIQl-ITE, 0F KIEL, GER- MANY, ASSIGNOES TO SIGNAL GESELLSCHAFT MIT BESCHRANKTER HAFT'UNG, OF

EIEL, GERIVIANY, A FIR-M.

soonoconnocrme TUBE.

Application filed August 25, 1921.

1 0 aZZ 2071 am it may concern:

Be it lantw'rn that we, annin Hal-inn- MANN and Pr ce Lioirrn, citizens of the German Republic, and residing at Kitsch-erg, near Kiel, and at Kiel, county o'l? Schleswig- Holstein, State of Prussia, Germany, have invented certain new and uselul Improve ments in SoundConductin Tubes, of which the following isa specification;

In ordinary sound-conducting tubes in which sound is to be conducted over considerable distances (say more than 10 yds.) the sectional area of the tubes must not be made smaller than a certain amount it the sound losses caused by the tube shall not exceed the permissible extent. The requisite cross sections of the tubes are quitc'considerable and approximate the size of the human concha. in transmitting sound energy from such tubes to the narrow auditory duct oi the ear most of the sound that arrives will, it the ear is simply placed against the open end of the tube, be reflected, because a considerable congestion of the moving air will take place at the point where the sound conduit suddenly becomes narrow. The same would occur it a wide tube wer caused to abruptly enter into a narrow piece of tube led to the ear.

The problem of conducting sound waves of a definite frequency, such as are employed tor instance in submarine sound signalling in an etlicient manner from a wide tube into a narrow tube (such as the narrow auditory duct of the ear) is solved by the invention in two ways.

The first solution consists in inserting a tapering connecting conduit of considerable length between the wide tube and the ear, theinside diameter ol the one end of the tapering conduit being adapted to the section of the wide tube and the inside diameter of the other end of the said conduit being made to match with the opening of the auditory duct. Experiments have proved that there is a certain most favorable length for the tapering part of the sound conduit. A short tapering piece will still produce a considerable reflecting et'l'ect and a tapering piece that is too long will be too narrow at its slender end to be an efticient conductor of sound, so that an increased loss of sound energy will arise in this way. The optimum condition are bes e p d a a fun i n Serial No. 495,232.

of the wave length of the sound for the transmission of which the tube is chiefly used. Ihe optimia'i length of the tapering conduit is about three times the length of the waves of the sound to be transmitted. Thus it sound waves vibrating at the rate of 1000 per second are to be transmitted, as

is often the case in sound signalling, the

tapering conduit should be about 1 metre in length. i

The second way of solving the problem consists in interposing between the wire tube and the ear a special, small, air resonator,

which is tuned to the pitch of the sound. 7

or a vibrating diaphragm which would pret.

erably be tuned to the sound to be trans mitted. I

Examples of the manner in which the invention may he carried out in practice are shown in the drawing in which,

Figl shows a longitudinal section oi a tube fitted with a tapering connecting piece,

Figs. 2, 3 and lillustrate sound boxes interposed between the tube and the ear,

Fig. 2 being provided with an earpiece,

Fig. 3 with an olive, and

Fig. 4 a slender pipe for the auditory duct.

The sound conducting tube 1, Fig. 1,

through which the sound arrives from the sound apparatus which may be any suitable known ClGXlCG, capable of emitting tones of substantially definite frequency, merges at a certain distance from the actual earpiece into the tapering interposed section or tube 2 the narrow openingo't' which is connected to a piece of flexible pipe 3 that terminates in an olive ladapted to be introduced into the auditory duct.

In the exan'iples shown in Figs. 2, 3 and a a resonating chamber or box 5 is connected to the main tube 1, the interior space of the box being very small and tuned to the sound employed or to the sound frequency principally occurring when the equipinent is used. In the arrangements shown in Figs. 2 and 3 the boundary between the resonating chamber 5 of the sound boX and the tube is formed by a vibrating diaphragm 6 Which is preferably also tuned. In Fig. & the space in the tube 1 is separated from the chamber 5 by a rigid Wall 7 with an opening 8 through \vnieh the air in the chain ber 5 is excited or set vibrating. The sound is conducted to the ear directly through the opening 9 in the chamber 5 in the ease of Fig. 2, and through a flexible pipe 3 in the cases of Figs. 3 and 4.

lVe claim 1. A sound conduit for conducting sound of a substantially definite frequency, comprising several portions, each of uniform cross-sectional area but of Widely different cross-section lQldiJiVQlY to the other portion, in combination with means disposed between said portions and dimensioned in ac cordanee with the particular Wave length of the sound transmitted and adaoted to transfer substantially the entire sound energy from one of said portions to the other.

2. A sound conduit for conducting sound of a'suhstantially definite frequency, comprising several portions, each of uniform cross-sectional area but of Widely different cross-section relatively to the other portion, in combination with a tube connecting said portions and gradually tapering from the large to the small cross-section and having its length dimensioned substantially three times the Wave length of the sound transmitted, said tube adapted to transfer substantially the entire sound energy from one of said portions to the other.

In testimony whereof We affix our signatures.

VALIER HAHNEMANN. HUGO LICHTE. 

